Field of the Invention
The invention relates to a centrifuge for separating a sample in the fields of medicine, pharmacy, genetic engineering, biotechnology, and so on, and particularly relates to improvement of a rotating shaft structure for use in a centrifuge with a swing type rotor and a sample container for the centrifuge.
Description of Related Art
A centrifuge is a device, which includes a rotor capable of housing a plurality of sample containers filled with samples therein and a driving means, such as a motor, rotationally driving the rotor in a rotor chamber, and rotates the rotor at a high speed to apply a centrifugal force, so as to centrifugally separate the samples in the sample containers. Centrifuge rotors can be roughly divided into two types, i.e. angle rotor and swing rotor. In the case of the angle rotor, a plurality of sample containers filled with samples therein are housed in housing holes, and a lid is fastened to the rotor above the opening parts of the housing holes for windage loss reduction and prevention of scatter of the samples and container debris when the sample containers break or deform. The housing holes are formed at a certain fixed angle with respect to the driving shaft, and the relative angle between the housing holes and the driving shaft is fixed at all times regardless of the centrifugal force.
In contrast, the swing rotor has a structure that the sample container filled with the sample is housed in a bucket, which has a bottomed part, and sealed by the lid covering the inside of the bucket and a sealing member, such as an O-ring, at a contact surface between the sample container and the lid, and a rod-shaped or convex rotating shaft disposed on the bucket or the lid is engaged with rotating shaft engagement grooves formed on the rotor, so as to dispose the bucket in the rotor in a swingable manner to perform centrifugal separation. The central axis of the bucket and the driving shaft of the motor are parallel to each other (θ=0°) when the rotor is stationary. However, as the rotation speed increases, the bucket disposed in the swingable manner is affected by the centrifugal force to rotate around the rotating shaft so that θ>0°, and then becomes substantially horizontal (θ≈90°) when a rotation speed that generates a centrifugal force sufficient to make the bucket horizontal is reached. Thereafter, the centrifugation operation ends, and θ decreases as the rotation speed drops and becomes 0° (θ=0°) when the rotation of the rotor stops. Thus, the relative angle between the central axis of the bucket and the driving shaft of the swing rotor changes according to the centrifugal force during the centrifugation operation. In addition, there are mainly two types of forms for holding the centrifugal load of the bucket during the centrifugation operation of the swing rotor. One form is that the convex parts of the rotating shaft disposed on the rotor or the bucket are received by the opposing concave parts and the load caused by the centrifugal force of the bucket is held only by the convex parts or the concave parts. The other form is that the bucket is swung to the horizontal by the rotating shaft disposed on the rotor or the bucket, and from there, the rotating shaft is bent to seat the bucket on a wall surface of the rotor, such that the load caused by the centrifugal force of the bucket is held by the rotor body (see Patent Literature 1, for example).